1. Field of Invention
Detergent bars.
2. Description of the Prior Art
The ideal toilet bar should have certain characteristics. For example, a toilet bar should possess good detergency when used on the skin and other surfaces in all kinds of water including hard, soft, sea, cold and hot. It should also exhibit excellent lathering qualities in all types of water and be mild and non-injurious to the skin. It should also have a pleasing appearance, rinse off easily and have a pleasing feel after use. The toilet bar itself should exhibit little or no tendency toward softening, blooming, crystallizing, cracking, drying or decomposing under storage conditions, and further have the ability to be produced in standard soap-making equipment.
Toilet bars prepared from soap have many of the aforementioned qualities, but as a class generally are deficient in one or more aspects and particularly with regard to lathering qualities under varying water conditions.
The addition of a synthetic detergent to soap to improve performance in hard and cold water has been practiced for many years, but the major objection to such combinations still resides in lather characteristics.
On the other hand, bars made principally of non-soap synthetic detergent are not satisfactory due to high hydroscopicity, unsatisfactory solubility characteristics, extreme defatting action on the skin, and lack of lubricant effect usually associated with soap, poor working properties in standard soap machinery, brittleness and poor cohesion or excessive softness of the bar itself. For example, alkyl benzene sulfonates are in general excellent from the standpoint of being able to produce lather in hard water, but, when used by themselves, result in detergent bars which are much too soft and sticky. Accordingly, in order to correct these deficiencies, the prior art suggests incorporation of various binders and fillers; however, bars so prepared still do not have the feel and other properties desirable in a toilet bar. In addition, bars made containing such constituents are difficult to process in conventional equipment.
Normally alkene sulfonates made by adding SO.sub.3 to an .alpha.-olefin, although being much harder than alkyl benzene sulfonates, become very sticky when small percentages of water are incorporated in a formed detergent bar. As a consequence, bars made from these materials are also very difficult to process in the usual soap-making equipment, and additionally have a tacky after-feel on the hands and also exhibit a wear rate which is extremely high, and thus are undesirable notwithstanding the fact that the lather evolved is of excellent quality.
Other synthetic detergents such as alkyl sulfates, sarcosinates, mono-alkyl succinates, coco methyl tauride and the like, although offering many advantages, are either too harsh in the ranges that they lather, require critical conditions to plod successfully, or are too expensive to be used as the main ingredient in detergent bars.
The alkane sulfonates, particularly in the C.sub.8 -C.sub.18 molecular weight range have also been suggested for use in detergent compositions. These materials are hard, at least as mild as soap, and will tolerate up to 25% water without becoming sticky. When used by themselves, however, even with 25% water these materials do not possess the desired plasticity characteristic of soap. Thus, they are difficult to process in that they are too hard to plod and stamp successfully. Moreover, the quality of lather evolved leaves much to be desired in volume and in creaminess. In order to correct these defects, the prior art (Canadian Pat. No. 636,022; U.S. Pat. No. 3,442,812; and U.S. Pat. No. 2,781,321) suggests incorporation in addition to the primary alkane a fatty acid plus other optional ingredients. It has been found, however, that when toilet bars are prepared in accordance with this prior art, the resulting product suffers severely in lathering characteristics and may be quite mushy.